JP2017053810A - Current sensor and measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sufficiently reduce the influence of an external magnetic field without reducing the detection sensitivity for a magnetic field generated when current flows through a measuring object.SOLUTION: A current sensor includes a sensor unit having a magnetic core 31 and an FG coil portion 33, and detects the current flowing through a measuring object in a state in which the sensor unit is disposed annularly to surround the measuring object. The current sensor includes the magnetic core 31 and the FG coil portion 33, a shield plate 37a disposed on the inner peripheral surface side of the magnetic core 31, a shield plate 37b disposed on the outer peripheral surface side, and shield plates 36a and 36b disposed on both lateral surface sides. The shield plate 37b is made of a second material having a magnetic permeability lower than that of a first material forming the shield plate 37a.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a current sensor configured to include a magnetic core, a magnetic detection element, and a shield member, and a measuring device configured to include the current sensor.

  As a measuring device provided with this type of current sensor, the applicant has disclosed a current measuring device 1 including a measuring device main body 2 and a current sensor 3 in the following prior application. In the following description, the components of the current measuring device 1 disclosed by the applicant in the following prior application are distinguished from the components of the current measuring device 1 described later according to the present invention. An explanation will be given with “x” attached.

  In this case, the current sensor 3x of the current measuring device 1x disclosed by the applicant includes a pair of sensor parts 22ax and 22bx (clamping part 22x) formed in a semi-annular shape so that the measuring object X can be clamped. The sections 22ax and 22bx are configured to include semi-annular sensor bodies 24ax and 24bx each having a winding 26x wound around the magnetic flux detection section 25x. The magnetic flux detection unit 25x includes a magnetic core 31x attached to the core holder 32x, an FG winding unit 33x, and the like, which are surrounded by shield plates 36ax, 36bx, 37ax, 37bx and are shielded from an external magnetic field.

  Thereby, in the current measuring device 1x (current sensor 3x) disclosed by the applicant, the magnetic flux induced in the magnetic core 31x by the magnetic field generated around the measurement target X clamped by the clamp unit 22x is transmitted to the FG winding unit 33x. When the current flowing through the measurement target X is detected by detecting by the above, it is possible to reduce the influence of the magnetic field generated in a live line or the like other than the measurement target X (a magnetic field generating source not clamped by the clamp unit 22x). It is possible.

Prior application 1

  Japanese Patent Application No. 2014-167239

  However, the current sensor 3x of the current measuring device 1x disclosed by the applicant has the following problems to be improved. That is, in the current sensor 3x disclosed by the applicant, the magnetic core 31x is surrounded by the shield plates 36ax, 36bx, 37ax, and 37bx to be magnetically shielded, so that the influence of the magnetic field from the magnetic field generation source other than the measurement target X is exerted. The structure which reduces is adopted. In this case, the current sensor 3x disclosed by the applicant has sufficient detection sensitivity for the magnetic field (magnetic flux) generated in the measurement target X clamped by the clamp portion 22x, and generates a magnetic field other than the measurement target X. In order to reduce the influence of the magnetic field from the source, as an example, each shield plate 36ax, 36bx, 37ax, 37bx is formed of permalloy PC.

  On the other hand, when measuring a current value using this type of “current sensor”, a magnetic field generation source (such as a power cable carrying a large current value) generating a strong magnetic field is located near the measurement target X. May exist. When measuring the current flowing through the measurement target X clamped by the current sensor 3x in such a measurement environment, an accurate measurement value is obtained under the influence of the magnetic flux induced in the magnetic core 31x by the external magnetic field. May become difficult.

  However, in order to reduce the influence of the external magnetic field at the time of measurement under the measurement environment as described above (in order to improve the magnetic shield capability), each shield plate 36ax, 36bx, 37ax, and the like shields the magnetic core 31x. It is also conceivable to form 37bx with a material having a lower magnetic permeability than Permalloy PC (a material that is hard to be magnetically saturated). However, in such a configuration, although the magnetic flux induced in the magnetic core 31x by the external magnetic field decreases, the magnetic flux induced in the magnetic core 31x by the magnetic field generated by the current flowing through the measurement target X also decreases. It may be difficult to accurately measure the current value flowing through the target X. Therefore, it is preferable to improve this point without reducing the measurement accuracy of the current value.

  The present invention has been made in view of such a problem to be improved, and a current sensor that can sufficiently reduce the influence of an external magnetic field without lowering the detection sensitivity of a magnetic field generated when a current flows through a measurement target. And it aims at providing a measuring device.

  In order to achieve the above object, the current sensor according to claim 1 includes a sensor unit having a magnetic core and a magnetic detection element, and the sensor unit surrounds the measurement target and flows through the measurement target in a ring shape. A magnetic sensor and a magnetic detection element, an inner peripheral surface side shield member disposed on the inner peripheral surface side of the magnetic core, and an outer peripheral surface side of the magnetic core. An outer peripheral surface side shield member provided, and a pair of side surface shield members respectively disposed on both side surfaces of the magnetic core, than the first material forming the inner peripheral surface side shield member The said outer peripheral surface side shield member is formed with the 2nd material with low magnetic permeability.

  According to a second aspect of the present invention, in the current sensor of the first aspect, the both side shield members are each formed of the second material.

  Furthermore, in the current sensor according to claim 3, in the current sensor according to claim 1 or 2, permalloy PC is used as the first material, and permalloy PB is used as the second material.

  According to a fourth aspect of the present invention, there is provided a measuring apparatus comprising: the current sensor according to any one of the first to third aspects; and a measuring unit that measures a current flowing through the measurement object based on a detection result by the current sensor. It is prepared for.

  The current sensor according to claim 1, wherein the current sensor is formed of a second material having a lower magnetic permeability than the first material forming the inner peripheral surface side shield member disposed on the inner peripheral surface side of the magnetic core. The outer peripheral surface side shield member is disposed on the outer peripheral surface side of the magnetic core. According to a fourth aspect of the present invention, there is provided a measuring apparatus comprising the above current sensor. Therefore, according to the current sensor according to claim 1 and the measuring device according to claim 4, the outer peripheral surface side is suppressed while suppressing a decrease in detection sensitivity by relatively increasing the magnetic permeability of the inner peripheral surface side shield member. Since the influence of the external magnetic field can be suppressed by relatively reducing the magnetic permeability of the shield member, the current flowing through the measurement target can be accurately measured.

  Further, according to the current sensor of claim 2 and the measuring device configured to include the current sensor, the influence of the external magnetic field is further reduced by forming the both side shield members with the second material. Therefore, the current flowing through the measurement object can be measured more accurately.

  Furthermore, according to the current sensor according to claim 3 and the measuring apparatus configured to include the current sensor, the use of permalloy PC as the first material and permalloy PB as the second material Since each shield member can be made of a material that is relatively inexpensive and easily available, a current sensor and a measuring device that can accurately measure the current flowing through the measurement object without causing an increase in manufacturing cost Can be manufactured.

1 is a configuration diagram showing a configuration of a current measuring device 1. FIG. 2 is an external perspective view of a current sensor 3. FIG. FIG. 4 is an external view of sensor bodies 24a and 24b in the clamp portion 22. 3 is an external perspective view of a magnetic flux detection unit 25. FIG. 3 is an exploded perspective view of a magnetic flux detection unit 25. FIG. It is sectional drawing of the sensor main bodies 24a and 24b.

  Hereinafter, embodiments of a current sensor and a measuring device will be described with reference to the accompanying drawings.

  The current measuring device 1 shown in FIG. 1 is an example of a “measuring device”, and includes a measuring device main body 2 and a current sensor 3, and is similar to the current measuring device 1x disclosed by the applicant in the above-mentioned prior application. The current value of the current flowing through the measurement target X clamped by the current sensor 3 can be measured in a non-contact state with respect to the measurement target X.

  The measurement apparatus main body 2 includes a measurement unit 11, an operation unit 12, a display unit 13, a control unit 14, and a storage unit 15, and a current value of a current flowing through the measurement target X via the current sensor 3 connected to the measurement unit 11. It is configured to be measurable. The measuring unit 11 is an example of a “measuring unit”, and when the current is supplied to the measurement target X clamped by the current sensor 3 according to the control of the control unit 14, as described later, from the current sensor 3. Based on the output detection signal (an example of “detection result by current sensor”), the current value of the current supplied to the measuring object X is measured. Since the principle of measuring the current value using a “clamp-type current sensor” such as the current sensor 3 is well known, detailed description thereof is omitted.

  The operation unit 12 includes various operation switches for performing a measurement condition setting operation, a measurement start instruction operation, and the like, and outputs an operation signal corresponding to the switch operation to the control unit 14. The display unit 13 displays the measurement result (current value) and the like by the measurement unit 11 under the control of the control unit 14. The control unit 14 controls the current measuring device 1 as a whole. Specifically, the control unit 14 controls the measurement unit 11 to execute a current value measurement process, and causes the display unit 13 to display the measurement value (current value) based on the measurement result of the measurement unit 11. . The storage unit 15 temporarily stores the calculation result of the control unit 14 and the measurement result of the measurement unit 11.

  On the other hand, the current sensor 3 is an example of a “current sensor”, and includes a grip portion 21, a clamp portion 22, and a connection cable 23 as shown in FIG. The grip part 21 is a part gripped by the user when the measuring object X is clamped by the clamp part 22, and the clamp part 22 is disposed on one end part side (left end part side in the figure). A signal processing circuit board (not shown) for generating a detection signal (a voltage signal proportional to the current value of the current supplied to the measurement target X) corresponding to the detection result by 22 is accommodated in the signal processing circuit board. The connected connection cable 23 is pulled out from the other end side (the right end side in the figure). In addition, the grip portion 21 is provided with an opening / closing operation portion 21 a for opening / closing the clamp portion 22.

  The clamp unit 22 includes a pair of sensor units 22a and 22b that are formed in a semicircular shape when viewed from the front and configured to clamp the measurement target X. The sensor units 22a and 22b are an example of “sensor unit”, and as shown in FIG. 3, a winding 26 is wound around the magnetic flux detection unit 25 (sensor parts: see FIGS. 4 and 5). Semi-annular sensor main bodies 24a and 24b are respectively accommodated in a resin case (not shown), and both sensor portions 22a and 22b are configured to surround an electric wire or the like of the measurement target X to form an annular shape.

  As shown in FIG. 5, the magnetic flux detection unit 25 includes a magnetic core 31, a core holder 32, an FG (flux gate) winding unit 33, a spacer 34, an insulating sheet 35, shield plates 36a, 36b, 37a, 37b, and a cover. 38a and 38b are provided. The magnetic core 31 is an example of a “magnetic core” and includes half bodies 31 a and 31 b that are arranged in a semicircular shape in the core holder 32. In this case, as an example, the half halves 31a and 31b are formed by laminating a plurality of magnetic thin plates made of permalloy PC, and the core holder 32 so that a gap G is formed between the halves 31a and 31b. It is housed and positioned.

  The core holder 32 includes a holder body 32 a that can accommodate the magnetic core 31 (half bodies 31 a and 31 b) and the FG winding portion 33, and a lid body 32 b that can be attached to the core holder 32. The FG winding portion 33 is an example of a “magnetic detection element”, and is a holder that is positioned in the vicinity of the gap G in the magnetic core 31 (between both halves 31 a and 31 b) attached to the core holder 32. It is attached to the main body 32a. The FG winding portion 33 is in a state in which the end portions of the sensor portions 22a and 22b are close to each other so that the sensor portions 22a and 22b surround the measurement target X and form an annular shape (the clamp portion 22 shown in FIG. 3). The magnetic flux induced in the magnetic core 31 by the magnetic field generated around the measurement target X when the current is supplied to the measurement target X in a state in which the measurement target X is positioned on the inner side can be detected.

  The spacer 34 is attached to the holder main body 32a together with the FG winding portion 33 to prevent the FG winding portion 33 from being detached from the holder main body 32a. The insulating sheet 35 is a member for increasing the insulation distance between the winding and the shield plate 36a in the FG winding portion 33 attached to the holder body 32a and improving the insulation between the winding and the shield plate 36a. The holder body 32a and the shield plate 36a are sandwiched. The shield plates 36a, 36b, 37a, and 37b are disposed so as to cover the core holder 32 in a state where the magnetic core 31 and the FG winding portion 33 are attached, so that the magnetic core 31 and the FG winding portion 33 are connected to the external magnetic field. Shield from.

  Specifically, the shield plates 36a and 36b are an example of “a pair of side surface shield members”, and as an example, a semi-annular magnetic thin plate formed of “Permalloy PB” as a “second material”. Are stacked in a plurality (three in this example). As shown in FIG. 6, the shield plates 36 a and 36 b are arranged on both sides (lower and upper sides in the figure) of the core holder 32 to which the magnetic core 31 is attached (the magnetic core 31 is accommodated). In this state, it is accommodated in the covers 38a and 38b.

  The shield plate 37 a is an example of an “inner peripheral surface side shield member”. As an example, a magnetic thin plate formed of “Permalloy PC” as “first material” is formed on the inner peripheral surface of the core holder 32. It is configured to be bent in a semi-circular shape along. As shown in FIG. 6, the shield plate 37 a is accommodated in the covers 38 a and 38 b in a state of being arranged on the inner peripheral surface side (left side in the figure) of the core holder 32.

  Furthermore, the shield plate 37b is an example of an “outer peripheral surface side shield member”. As an example, a magnetic thin plate formed of “Permalloy PB” as the “second material” extends along the outer peripheral surface of the core holder 32. It is configured to be bent into a semi-annular shape. As shown in FIG. 6, the shield plate 37 b is accommodated in the covers 38 a and 38 b in a state of being arranged on the outer peripheral surface side (right side in the figure) of the core holder 32.

  In this case, the permalloy PB forming the shield plates 36a and 36b and the shield plate 37b is a magnetic material having a low permeability compared to the permalloy PC forming the shield plate 37a, that is, magnetically saturated. It is known that it is a difficult magnetic material (a magnetic material that is easily magnetized and has a large residual magnetic flux density (high coercive force)).

  As shown in FIG. 4, the covers 38a and 38b are configured to accommodate the core holder 32 (the magnetic core 31 and the FG winding portion 33) covered by the shield plates 36a, 36b, 37a, and 37b, and the magnetic core. Around the 31 (core holder 32), a plurality of flanges for preventing collapse are provided so as to function as a bobbin for winding the winding 26.

  In manufacturing the current sensor 3, first, the magnetic flux detection unit 25 is manufactured. Specifically, after the magnetic core 31 (half bodies 31a and 31b) is fitted into the holder body 32a, the lid body 32b is attached to the holder body 32a. Thereby, the magnetic core 31 (half bodies 31a and 31b) is accommodated and positioned in the core holder 32, and a gap G is formed between the half bodies 31a and 31b. Next, the FG winding portion 33 and the spacer 34 are attached in this order to the surface of the holder main body 32a opposite to the lid 32b. Thereby, the FG winding part 33 is positioned in a state where the FG winding part 33 is positioned in the vicinity of the gap G formed in the magnetic core 31 (between the half halves 31a and 31b).

  Subsequently, a shield plate 36a is disposed on the surface of the holder body 32a opposite to the lid body 32b (one side of both side surfaces of the magnetic core 31) with the insulating sheet 35 interposed therebetween, and the holder body of the lid body 32b. The shield plate 36b is disposed on the surface opposite to the side 32a (the other side of the both sides of the magnetic core 31), and the shield plate 37a is disposed on the inner peripheral surface of the core holder 32 (the inner peripheral surface side of the magnetic core 31). The shield plate 37b is disposed on the outer peripheral surface of the core holder 32 (the outer peripheral surface side of the magnetic core 31). Next, the core holder 32 (the magnetic core 31 and the FG winding portion 33) in which the shield plates 36a, 36b, 37a, and 37b are disposed is accommodated in the covers 38a and 38b. Thereby, as shown in FIG. 4, the magnetic flux detection part 25 is completed.

  Next, as shown in FIGS. 3 and 6, sensor bodies 24 a and 24 b are manufactured by winding the winding 26 around the magnetic flux detector 25 (covers 38 a and 38 b). The sensor parts 22a and 22b are manufactured by housing in a resin case. Thereafter, the completed sensor portions 22a and 22b are attached to the gripping portion 21, and the winding of the FG winding portion 33, the winding 26 and the connection cable 23 are respectively connected to the signal processing circuit board in the gripping portion 21. As shown in FIG. 2, the current sensor 3 is completed.

  When measuring the current value of the current flowing through the measuring object X using the current sensor 3, the connection cable 23 of the current sensor 3 is connected to the measuring unit 11 of the measuring apparatus main body 2, and as shown in FIG. The measuring object X is clamped by the clamp part 22 of the current sensor 3. Next, the measurement process is started by operating the operation unit 12 of the measurement apparatus main body 2. At this time, when a magnetic field is generated around the measurement target X due to a current flowing through the measurement target X, a magnetic flux is induced in the magnetic core 31 of the current sensor 3 by the magnetic field, and this magnetic flux is transferred to the FG winding. Detected by the unit 33. Therefore, based on the amount of magnetic flux detected by the FG winding part 33, the current value of the current flowing through the measuring object X is measured by the measuring part 11 of the measuring apparatus body 2.

  In this case, in the current measuring device 1 (current sensor 3) of this example, as described above, the shield plate 37a disposed on the inner peripheral surface side of the magnetic core 31 is formed of permalloy PC having a certain degree of magnetic permeability. ing. Therefore, in the same manner as the current measuring device 1x (current sensor 3x) disclosed by the applicant in the prior application, the detection of the magnetic field generated in the measuring object X located on the inner peripheral side of the magnetic core 31 is detected by the shield plate 37a. Therefore, it is possible to detect a magnetic field having a strength corresponding to the current value of the current flowing through the measurement target X without being greatly hindered by.

  In the current measuring device 1 (current sensor 3) of this example, as described above, the shield plate 37b disposed on the outer peripheral surface side of the magnetic core 31 and the shield disposed on both side surfaces of the magnetic core 31. The plates 36a and 36b are made of permalloy PB having lower magnetic permeability (perhaps less magnetically saturated) than permalloy PC. Therefore, for example, as shown in FIG. 1, even if a magnetic field generation source such as a live line Y exists outside the clamp portion 22 that clamps the measurement target X, the shield plate 37b and the shield plate 36a 36b, the magnetic core 31 is suitably shielded against the magnetic field from the live line Y, so that the influence of the magnetic field generated in the live line Y is sufficiently reduced.

  Thus, in this current sensor 3, a “second material” having a lower magnetic permeability than the “first material” forming the shield plate 37 a disposed on the inner peripheral surface side of the magnetic core 31. The formed shield plate 37 b is disposed on the outer peripheral surface side of the magnetic core 31. In addition, the current measuring device 1 includes the current sensor 3 described above. Therefore, according to the current sensor 3 and the current measuring device 1, while reducing the detection sensitivity by relatively increasing the magnetic permeability of the shield plate 37 a as the “inner peripheral surface side shield member”, the “outer peripheral surface” Since the influence of the external magnetic field can be suppressed by relatively reducing the magnetic permeability of the shield plate 37b as the “side shield member”, the current flowing through the measurement target X can be accurately measured.

  In addition, according to the current sensor 3 and the current measuring device 1, since the shield plates 36a and 36b are formed of the “second material”, the influence of the external magnetic field can be further reduced. Can be measured more accurately.

  Furthermore, according to the current sensor 3 and the current measuring device 1, the use of permalloy PC as the “first material” and the use of permalloy PB as the “second material” makes it relatively inexpensive and easy. Since each shield plate 36a, 36b, 37a, 37b can be manufactured with an available material, the current sensor 3 capable of accurately measuring the current flowing through the measurement target X without causing an increase in manufacturing cost The current measuring device 1 can be manufactured.

  Note that the configurations of the “current sensor” and the “measuring device” are not limited to the configuration examples of the magnetic flux detection unit 25, the current sensor 3, and the current measuring device 1. For example, an example in which permalloy PC is used as the “first material” and permalloy PB is used as the “second material” has been described, but the “first material” and the “second material” are examples of this example. The “shield member” can be formed of various magnetic materials within a range that satisfies the condition that the permeability of the “second material” is lower than the permeability of the “first material”. . Specifically, as an example, an arbitrary set of magnetic materials satisfying the above conditions is selected from various magnetic materials such as Permalloy PC, Permalloy PB, amorphous magnetic material, and silicon steel plate, and each “shield member” is selected. Can be formed.

  Further, the example in which the shield plate 37a is formed of “first material (Permalloy PC)” and the shield plates 36a and 36b and the shield plate 37b are formed of “second material (Permalloy PB)” has been described. The shield plates 36a and 36b corresponding to the “side shield members” are formed of “first material (for example, permalloy PC)” or “first material” and “ It can also be formed of a “third material” different from any of the “second materials”. In this case, when the shield plates 36a and 36b are formed of the “third material”, the magnetic flux detection described above is adopted by adopting a material having a lower magnetic permeability than the “first material” as the “third material”. Similarly to the unit 25, the current sensor 3, and the current measuring device 1, the influence of the external magnetic field can be sufficiently reduced, and the current value of the current flowing through the measurement target X can be accurately measured.

  Furthermore, although the example which employ | adopted FG coil | winding part 33 (flux gate winding) as a "magnetic detection element" was demonstrated, it replaced with such a structure and "windings", such as the coil | winding 26, were "magnetic detection element." Or a Hall element or the like as a “magnetic detection element” (not shown). In addition, a “current sensor” can be configured by including a plurality of “magnetic detection elements”. For example, a zero flux type current sensor can be configured by adopting a configuration in which the FG winding portion 33 and the winding 26 are used as “magnetic detection elements”, respectively.

  Further, the current measuring device 1 in which the measuring device main body 2 (measuring unit 11) and the current sensor 3 are separately described has been described as an example. However, the configuration of the “measuring device” is not limited to this, and the “measuring unit” The housing (measuring device main body 2 and gripping portion 21 in the current measuring device 1) and the “current sensor” can be configured integrally (not shown). Even in such a configuration, the current value of the current flowing through the measuring object X can be accurately measured by sufficiently reducing the influence of the external magnetic field in the same manner as the current measuring apparatus 1 described above. In addition, the configuration of the current sensor 3 including the pair of sensor units 22a and 22b has been described as an example. However, the “current sensor unit” is not limited to the “clamp type current sensor”, Also in the “current sensor”, the current flowing through the “measurement target” can be accurately measured by forming each “shield member” with a magnetic material satisfying the above-described conditions.

DESCRIPTION OF SYMBOLS 1 Current measuring apparatus 2 Measuring apparatus main body 3 Current sensor 11 Measuring part 22 Clamp part 22a, 22b Sensor part 25 Magnetic flux detection part 31 Magnetic core 31a, 31b Half body 32 Core holder 33 FG winding part 36a, 36b, 37a, 37b Shield plate X Measurement target

Claims (4)

A current sensor that includes a sensor unit having a magnetic core and a magnetic detection element, and that detects a current flowing through the measurement target in a state where the sensor unit surrounds the measurement target and forms an annular shape,
The magnetic core and the magnetic detection element, and an inner peripheral surface side shield member disposed on the inner peripheral surface side of the magnetic core, an outer peripheral surface side shield member disposed on the outer peripheral surface side of the magnetic core, And a second material having a pair of side surface shield members respectively disposed on both side surfaces of the magnetic core, and having a lower magnetic permeability than the first material forming the inner peripheral surface side shield member. A current sensor in which the outer peripheral surface side shield member is formed.   The current sensor according to claim 1, wherein the both side shield members are each formed of the second material.   The current sensor according to claim 1 or 2, wherein permalloy PC is used as the first material and permalloy PB is used as the second material.   A measuring apparatus comprising: the current sensor according to claim 1; and a measuring unit that measures a current flowing through the measurement object based on a detection result of the current sensor.

Images